Fix test on user->id

htdocs/user/class/user.class.php

@@ -835,6 +835,12 @@ class User extends CommonObject
 
 		dol_syslog(get_class($this)."::addrights $rid, $allmodule, $allperms, $entity, $notrigger for user id=".$this->id);
 
+		if (empty($this->id)) {
+			$error++;
+			$this->error = 'Try to call addrights on an object user with an empty id';
+			return -1;
+		}
+
 		$error = 0;
 		$whereforadd = '';